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Hubble astronomers have uncovered, for the first time, a population
of infant stars in the Milky Way satellite galaxy, the Small
Magellanic Cloud (SMC, visible to the naked eye in the southern
constellation Tucana), located 210,000 light-years away.

Hubble's exquisite sharpness plucked out an underlying population of
infant stars embedded in the nebula NGC 346 that are still forming
from gravitationally collapsing gas clouds. They have not yet ignited
their hydrogen fuel to sustain nuclear fusion. The smallest of these
infant stars is only half the mass of our Sun.

Although star birth is common within the disk of our galaxy, this
smaller companion galaxy is more primeval in that it lacks a large
percentage of the heavier elements that are forged in successive
generations of stars through nuclear fusion.

Fragmentary galaxies like the SMC are considered primitive building
blocks of larger galaxies. Most of these types of galaxies existed far
away, when the universe was much younger. The SMC offers a unique nearby
laboratory for understanding how stars arose in the early universe.
Nestled among other starburst regions with the small galaxy, the nebula
NGC 346 alone contains more than 2,500 infant stars.

The Hubble images, taken with the Advanced Camera for Surveys, identify
three stellar populations in the SMC and in the region of the NGC 346
nebula  a total of 70,000 stars. The oldest population is 4.5 billion
years, roughly the age of our Sun. The younger population arose only 5
million years ago (about the time Earth's first hominids began to walk
on two feet). Lower-mass stars take longer to ignite and become
full-fledged stars, so the protostellar population is 5 million years
old. Curiously, the infant stars are strung along two intersecting lanes
in the nebula, resembling a "T" pattern in the Hubble plot.

The observations, by Antonella Nota of the European Space Agency (ESA)
and the Space Telescope Science Institute (STScI), Baltimore, Md., are
being presented today at the meeting of the American Astronomical Society
in San Diego, Calif.